Screw propeller



Aug. 25, 1931. v. LoUGHEl-:D

SCREW PROPELLER Filed May 20, 1929 3 SheetSr-Sheec 2 y I/vvf/vro/e. @EL e l l//cTo/e Loue/#EE0 BYMW^ Ange/wr All@ 25 1931- v. LOUGHEED 1,820,814

SCREW PgoPELLER Filed May 20, 1929 3 Sheets-Sheet 3 [NVE/Woe.

l//cToR L Que/1550 *m1, B Y a ATTa/@Ms Y Il the centrifugal force', re

it of rotation and whic through itssurface A f 4 -pear more liatented Aug. 25, 1931' "vieron Loveannu, or wasnmeron, Drsrarc'r or commun scaEw rnorm.m

`Application led Iay 20, 1929. Serial No. 364,538.

This application is in part a continuation of my earlier application' Serial 'Number 296,610, filed Julyl, 192,8, for screw propellers.

5 My invention'relates broadly to screw propellers and more particularly to reversible ypitch propellers.

' The object of my invention is a simple and 'rug edly constructed propeller, the blades of Whic .are freely and unfailingly rotatable at the pilots will from one angular position to another by moderate muscular or other eiort.

' Another object of my invention is to pro- A duce a propeller the blades of which are ioated in a liquid 'which wi not only produce a substantially frictionles .-bearingsurface but will also-exert`.upon the blade a pressure radially inward toward the hub of the pro; Y peller in an' amount substantially equal to 2' the centrifugal force of the blades when in rotation.

, A further object of my invention is to 'so construct a propeller of this type that the force exerted upon the blades of the propeller by the liquid .and tending to force the blade toward vthe center of rotation so that the blade flotation'at all times is substantially constant irrespective of the speed of the revof lut'ion of the propeller.

80 A `further ob'ect of my invention is to balance the centri ugal component in each vblade and attached elements by an opposing centripetal force, which at all times can be madeto actisubstanti'ally equally andoppositely to -I dless of the velocyo opposition introduces no ap reoiable friction to the actuating means.'

Further b'ects' of m invention will apy hereina Y r as the description .f the method and a paratus is'developed.

The v prob em is variable-pitch and reversi le-bla ev propeller des' 1s conse- 4'quent upon the extreme magnitii e 'of the cenl trifugalfo'ces'acting topull the blades out ofthe 1mb.y A

.Centrifu force, .which with an air proi 'peller turmng-at.1,800 revolutions a minute,

y for example, and witha blade weight'of 20 funds regarded being 10cm; ending of feet from the center of rotation, reaches a value of over 33 tons, is so great that even the most-eiicient ball and roller bearings the sizes and weights of such bearings adequateto carry the loadare prohibitive. Moreover, the energy requisite to Iproduce angular rotation of the blades, mounted even 1n the best of su'ch anti-friction bearings, Iwith the propeller turning at full speed 1s. foundI to be much greater than any eifort it is reasonablyl possible to exert by hand, or through any remote-control servo mechanism except such as have been found too massive or complicated to be practical.

This force, so enormous in contrast even to .the maximum weights and proportions al- 'lowable in the parts of an aviation-propeller, heretofore has defeated every attempt' to provide bearings really adequate to car it, and yet light enough in'wei'ght and of s cientlyow friction coeilicient to permit angular blade movement Aat the pilots will, without delay, and without unreasonable physical ef-r fort.

There are also lserious secondary roblems-of providing freel blade inova ility without introducing such looseness or lost motion as must permit vibration and thus occasion failure of the structural elements,

the materialsof which in established. pro ller ractioe arestressed uncomfortably c ose to t eir limits of strength;` and, generally, 'of building the hub and mounting the movable :fblades `in suchf-amannerl that -thelstructure cannot ily to pieces. A. v

My invention consists substantially in the construction, combination .and arrangement of parts associated in my improved propeller as will be more fullyhereinafter set forth as shown by the` accompanying drawings. and finall pointed out in the appended claims.

4Re erenee is to be had to the accompanyingdrawings forming a part of this specification in A which like reference )characters indicate corresponding parts throughout the several 5 views and in which Figures 1 and 2 are diagrammatic tions. of the pernciples upon which my inventioxii's foun i Figure 3- shows one blade ofaA two'bladed driving shaft, and with the essential inner elements pertaining to the upper bladecross such as mercury che and broken sectioned,\while the elements` for the lower blade are broken away. The blades proper are not shown, because they may be of any suitable form or construction, and because their form beyond the blade Shanks may vary with the design of the blade for any specific use. i

. Figure4 is a section on the line 4 4, Figure 3.

Figure 5 is a sectional view on the line 5-5 of Figure 4.

Figure 6 is a detail ating mechanism, and

`Figure 7 is a detail cross-sectional 'view of my invention as applied to a propeller for a ACurtiss drawn toscaleof an actual propeller subjected to test. 'y

Referring particularl to Figure 1, numeral ldesignates a prope er blade the radius of gyration of which with attached elements can be designated as v2 at the distance X from the center-of rotation 3. The blade carries` an annular float 4 surrounded by anannularl cup 5. This cup 5 is filled with a liquid 6 or liquid gallium so that under the static condition shown the blade 1 and its oat 4 are suspended by the weight ofthe liquid displaced. When the elements of the system are thus balanced, the liquid 6 view of my blade actuforms anannular iuctuation element' of U- shaped cross-section.

The float must be constituted of light metal or molded composition which will not amal` gamate with or be pervious to the mercury or the particular liquid used, and which must strong enough` to endure the crushing effect of hydrostatic pressure. It may be made either solid, as shown in Figure.3 of light material, or hollow as shown in 'Figure 7.l The possibility'is`contemplated of developing a. construction of thin-walled metal reinforced by' the use of wood inserts or some hard light plastic.

sition illustrated in Figure l.

, Instead, l`to balance out .the lcentrifugal force in the'blade when it isrevolved around' the center of 'rotation' 3, -an amountv of flotation must'be secured that, toz the wei htto be balanced, must be in the inverse ratio hat the distance from the center. of revolution 3 'to the to the distance from the samfe center of revo-v lution 3 to the radius of gyration 2 of the4 weightlof mercury used. Rather,l it isa func# `tlon ofthis weight plus the weight of mer-` longnose lWasp engine and is- It does not suice, however, for'the present purpose, merely to oat the propeller blades and attached elements statically in thel po Ijadius of gyration 7 of the' mercury Abears- Leaders of gyrationof the mercury factored into the velocity of lrevolution, factored into the radius. This centrifugal pressure will not involve as a factor the actual wei ht of the mercury-though ofcourse it does involve its specific gravity ordensity. Therefore with the annular cup 5 modified into the' form sketched in Figure 2, the pressure on the bot-Y tom 8 as well as against the other inside lower surfaces 9, vin accordance with Pascals law, will be the same for the same unit areafas it is in the receding case, under similar conditions of) centrifugal force,`and with the mercury depth of the mercury in Figure l.

This opposing pressure being the hydrostatic pressure of a confined liquid subjected to centrifugal force, its actual magnitude chiey' involves, not its mass but ^the areal against which'it acts, regarded as projected transversely to the blade axle. It-therefore concerns the height of the column' 10 or the amount of liquid displaced bythe float 4 rather than the cross-section of the column 10 or the amount of liquid that isleft surrounding the float 4, so theoretically the amount of liquid required can be reduced to an infinitely Asmall amount, and in actual practice to a verysmall quantity, the latter determined solely by'the closeness ofthe clearances it is mechanically practicalto machine and maintain between the float 4 and the cup trifugal force in the case of my invention calls for no intolerable weight increase in the mechanism. v l

T-he correctly-calculated quantitative conditions, fulfilled, therefore, the most minute quantity .of f mercury disposed in columns of proper height, or length,'between the cup or stator cylinder 5 and the float 4, and acted upon by centrifugal-force, will produce in the closed end of the stator cylinder 5 a hydrostatic pressure which, acting inwardly against [the bottom surface of the `float 4, can at all speeds of revolution exactly coun- 'teract or balance the centrifugal forcegin the length of the vertical column parallel to the column 10 of the same height as the 5. Hence :the balancing of the cen- 2110 ances there are to overcome to eect the freel angular rotation of the blade 1, the float 4, and the elements attachedfto them.,

Referring particularly to Figure 3, thehub proper designated as' 11.is seen -to be pierced `with* a tapered hole 12, for mounting on a standardsplined drivingshaft 13 o`f Figure 6. The threads shown at14 are for the application of a wheel puller, to'facilitate the yremoval ofthe hub from the shaft 13.

To this hub 11, accurately located by the steps turned in the matching contact faces 15, 'the cylindrical stator elements 16 are securely held by the locked-wired circles of' special ing radially outwardunder the influence of\ centrifugal `force. The rating of 'this bearing-is premised upon the thrust and torque loads developed in the propeller blade. This bearing does however in normal operation, as will presently appear, carry a very moder- 'ate thrust load directed centripetally, in-

\ ward, andcommunicated to its inner race by the flange 19. gk

Into a recess bored in the face shown of the hub 11, the outer race of the double-row, self-aligning, annular ball bearing 21 is itted with the usual sucking fit, while its inner race, as in the'case ofthe bearing 17 is made a light vpress fit o n the propeller-blade shank 18. This bearing should vbev of the same radial-load "capacity, underl the 1same condi@ tions of naught revolutions, as'that of bearin 17. It similarly carries radial` load on y.-except for a moderate'thrust load, outwardly, imposed against its outer race by the heavy laminated star springv22.

These two bearings serve accurately to cen- 'terfthe propeller-blade shank through the stator cylinder 16, and to take all radial loads upon rthe blade, which tend to move it out of center.

The bearing -17 is protected by the light pan-like cover 23, which is clamped between its inner race and the -iiange 19, so that it serves to exclude moisture and dirt, andto prevent the lubricant in the bearing from being centrifuged out, a similar pan-like cover J23a serving similar function forthe Aat 24 and 25 are soft feltfwashers to imi prove the closure against the egress of lubrig tapered cant and the ingress of water 'and dust, while at the'same time occasioning no appreciable friction to resist rotation. vThe wedging 'effect due to centrifugal force acting on these washers keeps them particularly tight while the propelleris in operation.

It's to be noted that the edges of the cover 23 and the contained felt washer 24 are of smaller diameter than the outer end 16a of thestato cylinder 16. Hence water or dirt falling or ice forming on the surface off16- tend to be thrown centrifugally past rather than against 23 and 24. A

At 26 is a helical spur-gear,I forced on the tapered diameter 27 of the blade Shank 18, -which is compelled vtol turn with it by two opposite woodruil keys,.the seat for `'one of which appears -at 28. One'of these' keys thicker than the other, this gear always must go in its original angular position.

- The blade shank 18 is milled to its -smallest diameter, at 29, and is embraced b the split collar 30, which is slightly tapere on its inner `face, whichftsagainst the similartaper of the groove 295m the blade shank 18. Hence when this split collar is tightly clamped by its bolts 31, the whole assembly is compelled to pull up snug, with no possible looseness. Thisis most important becausey the entire centrifugal load of the propeller blade and attached 'elements pulls against and is transmitted through this split collar 30, the shank cgmdition being essentf ally that of a bolt under tension, the stem diameter of the boltv being represented by the small diameter at 29while thebolt head is represented by the tapered annular ring 27 of the blade shank 18.

Replacement' of the split collar 30 always in the sam'e` angular position is insured by t e pin key`33, engaging with one of its halves. y

An undercut recess 34 turned in the split collar 30 engages a similar undercuton the O'ear 26 and thus precludes loosening and roppm'g, back of the latter on the taper.

Between theouter side of the s lit collar 30 farthest from the Ahub 11 and an .annular sholilder 36 on the vblade shank 18is an an? nular member which is lightly forced on the'tapered portion 38 of the blade shank 18. This taper is larger than, though of the same angle as that at 27, so that annular memberv 37 easily passes over the latter.

To this annular member or float carrier 37 is attached, by the lock-wire screws A38a the float 4, accurate-concentric locatlon being secured by the stepgroove at 39.

The annular member 37 1s maintained in fixed relation to the split collar 30 by means of a pin 40. In this manner theiiioat 4 iis JZB rigidlyailixed to the shank 18 of theblade 1. 'll of these precautions to preserve the.

. ori inal angular relationships of .the several' assembly elements are designed topre'serve `true concentric location of the float 4 within iso '20 sV closed by the stator cylinder 16 and to maintain'perfect alignment of the blade shank 18l 'with the axis of the stator cylinder 16.

The stator cylinder with the reentrant sec- 5 tion' 41 and the float 4 should bel absolutely,

out-of contact with each other at all times and at every point. These parts nevertheless are made to approach each other to the closest clearances v compatible with .reasonable machining accuracy and ish, Iconcentriclty and mounting of1 the Amembers of the bearings 17 and 21,allowance for any possible minute lost motion, and a proper consideration of the size-changing and distorting effects of expansion and contraction due to alterations in temperature. at which the prope'lllr may be exposed'. duced into the space through a hole which a small tapered screw plug 45a. Leakage of the mercury from its enclosing space, when the blade 18 is stopped with the stator cylinder 16 in an inverted position, .is effectively prevented by the compression of the rubber washers 42 and 43 in contact with the stator cylinder 16 and its reentrant portion 41, respectively, by the laminated star spring and bythe fact thatthey have only to oppose the very small hydrostatic pressure of a few inches of mercury acting against the exceedingly small area of ends of the clearance spaces 45 between the stator cylinder 16, the reentrant section 41 and the lioat 4. Referring particularly to Figures 3-6, numeral I designates the crankcase of an engine which carries my improvedl blade actuating mechanism, mounted around the driving shaft 13. This actuating mechanism, while an vessential component of my inven- 40. tion, is of principal present interest because it suggests how the light, quick-acting manual control, manipulated with only moderate effort, is applicable to'reverse blades of my propeller.

Within the stator cylinder 16 and close to the hub 11 is provided a rackshaft guide ring 53, with a close machine iit to thestator casing 16. Upon this guide ring are two bosses 54 carrying bearings, in.which are mounted rackshafts 56. -This rackshatt engages .the helical gear 26, as is clearly shown in Figure 4. U on the rackshaft` ring 53 and radially past t e point at which the rackshaft engages the helical gear 26, I have provided a bearing mounting 58, whichy carries either a ball bearing or a roller bearing, as shown at 59. This l roller bearing insures positive engagement of Y the rackshaft 56 with the helical gear 26 at 'all times, The friction that would result were mesh maintained solely by the plain sliding surfaces through the bosses 54: thus is considerably reduced, and. lostvmotion between the `gear and rack teeth minimized. Because the outer ends of the rackshafts, if

Iileft fully round,l could'n'ot passxthe gears e correct amount of .mercury is intro-` or vary the Leaders 26, when entered into the holes in 54, their tooth-bearing, sides are flattene'dof'to allow the requisite clearance. rlhen, after they are in place, with the propeller assembled on the shaft .13,the filler pieces 59 are appliedy Lo themand secured in place by the wired screws 59a..

The gears 26 and racks 56 are cut with helical. instead of with straight, spur teeth so as to maintain .at all times smooth progressive operation without backlash, lost motion, or Shifting of tooth leverage, which might cause vibration or blade Hutter. f

The crankcase 50'of the engine carries a cylindrical bearing housing 60 which is threaded as shown at 61. In engagement with these threads I haver provided a sleeve or .drum 62, which at its outer end and inner diameter bears slidabl and rotatably upon the housing 60. Upont e outer end and outer diameter of the sleeve 62 is fastened by spinning the inner race of the Ihe outer race of the ball bearing 63 is carried by an annular member 64 which carries the rack shafts 56, which engage thelgears 26 as shown in Figure `4. The outer surface of the sleeve 62 is grooved as shown 'at 65 to -enable positive engagement of cables 66 thereon.

The multipns, thread at 61 is of a pitch'high enough to aord .full traverse of the gears 26 by the rackshafts56, withonly a moderate ball bearing 63.

angular movement of the drum or sleeve 62- preferably lwith less than one full revolution.

At the same time the pitch is low enough lo lafford an irreversible mechanism-A-that is, end pressurefrom the rackshafts v56 cannot cause the drum or sleeve 62 to turn;

' The duplication in each ofthe cable pairs 66 is simplyto provide the utmost precaution against any element of the device failing.

Making the cable grooves 65 on the outer surface of the drum 66'of the same pitch as that of the multiple threads on its inside allows the cable pairs always to come from the same point 67 and lie at the same, angle to the pulley wheels 71 and 72 which direct the 'cables 66 tothe cockpit of the plane.

Because even the low rolling friction in` the bearing 'must tend to, turn the drum or sleeve 60 in the direction of rotation, and because of the further possibility of this bearing failing, and since the control lock on 'the cables 69 and 70 may be remote .from the drumy 62, I Ahave provided a. more positive lock in close have shown as alpawl ratchet 74, cut `in a flange 62a on the drum. The eiect of this pawl and v ratchet is to allow free rotation of the sleeve or drum 62 proximity to the drum to hold the drum 62 in any given position. This lock,

73,-engaging with i he in the direction opposite to that of thedriv.- A

ing shaft A13 but rotation in thesame direction as that of thewdriving shaft can occur only as a result of a pull on the cable pair 66, lthe tension of these cables, as soon as'it reaches a certain critical value, working a ainst the tension of the spring 75 and liftin the pawl 73 out'of engagement with the ratchet 74,

i remote point at which it is secured. The effect tion to the internal pressure exerted thereon,

as will be hereinafter described. The outer end 16a ofthe" stator ($5316 is formed with -of this, or of the breakage of the cables, is to slack the pair 69, with the result that the tensionA of the spring 75 positively forces the pawl 73 into theratchet 74 and prevents un# desired rotation.

As a still further precaution,` the direction of the thread 61, in its relation to thedirection of shaft rotation, is made such that any conceivable failure of the control means,

which might allow the sleeve or drum 62 to screw oif the housing 60, can progress onlyJto the point of increasino` the blade angles lto the maximum pitch the mechanismv is designed to allow, at which point the possibility of further motion is excluded by the abutment of the curved surface shown at 76 on -the rackshaft 56.

Referring to Figure 7 of which shows a cross-section of one hub element of my improved propeller, as developed for tests, numeral 13 designates a shaft of al Wasp long-nose engine,l which carries the. usual' lands 100 and wedged mounting memf bers 101. The numeral 11 designates the hub proper of my improved ropeller, whichl also 'carries lands and bla for engagement with .the lands and blanks upon shaft 13. This hub is securely mounted upon the shaft 13 by means of the wedge members 101 yand al threaded nut 102. My improved hub carries two yannular vrings 103 and 104. yThe annular member 103has stepped faces shown at 105, ,upon which is mounted a stator casing 16, secured thereto and located thereon by means of a circle ofwired capscrews 106 and dowelpins 107. The stator casing 16 as it radially extends outward from the hub graduall increases in thickness in propora shouldered extensi ally inward from the. larger diameter of the stator casing `16.

140 and an internal core 138,mach1ned intel The inner diameter offthis annular ring is stepped ftat 110 for engagement with a reentrant sleeve or member 41. The reentrant member is thickened atits outward portion to provide strength to resist the internal ressurej along the float 4 when the' pr y i ing. Around. this core 138 and ulkheads 139 thereon as will hereinafter be descri Thepertion 112 of the reentrant member 41 isr'thinned away as it .approaches the hub 11,

because the pressure isJ not so great at this point and o ne of the necessities in all propeller rconstructiefri-is to make a structure' as light asr practicable. -The extreme outer.l portion of [identical purpose as that of 24 of'Figure 3.

-'isprovided with the usual annular clamping Q18, into which is screwed a clamping memthe drawings, .sp

, of 104. The threaded member 124 carries a 4`pin 130,by\means of a resilientmember 133.

as shown at 109, and is made a press A This core.138 carries integrally therewith Qa plurality of bulkheads 139, saced from the reentrant member 41 is provided withv an annular sleeve 117 which serves as a mount' ing vfor the Jball bearing 114 which corresponds to the bearing 17 shown in Figure 3.

two packings 119 and 120 which serve an -The bearing race 116 fits upon the shank 18 of the standard propeller blade. This shank rings 122 and 123.

As shown, I have provided a screw threade ed depression 121 intothe base of the shank ber 124, which serves to hold the helical gear 26 securely in engagement with. the base of the propeller shank 18. This gear 26 is also of studs 127. The gear 26.carries an inner .the annular ring 104 of the, hub. Betweenv the rings 128 and 104 I havefplaced the bearing 21, held therein against a flange 129 by inning or crimping over of the outer edge bearing pin 130, which extends from member 124 along the axis of the shank 18 toward F the center of the shaftv13. Between the endof this bearing and the hub 11 I have mounted a ball 131 centered in a plate 132 which resiliently holds the balL131 against the end of the The opposite bearing surface for 'the ball 131 I have shown as a plug at 134spaced from the ball with a slight clearance as shown at v135. These elements serve the same function re 3. Around as the star spring y22 of Fi the shank 18 of the propel er blade andin .engagement with the annularring 122 and 123 are segmental elements 136 of the shape` shown. These elements 13 6are forced into the tapered bore'in\and against the seat on 137, which is an extension of or rigidly secured to the float 4. Thisoat extends between the stator casing 16 and'the reentrant member 41 with the minimum practicable clearance, sothat there is nefriction between lthe float 4, the stator casing and its reentrant member 41. `This oat is made up of a sleeve gral with the annular member 13 7.

each other distances correspon ng tothe welded to the core 138 at .points 141 and 142.` To assure. maintenance ofthe float 4 1n its `centralized positionbetween the stator ele# secured against torsion by means of a 'circle p v'centrifugal hydrostatic pressure gradient ller is turnexerted thereon 'by with a stiifened annular rib145, as shown.`

Thisannular rib 145 formslthe lrim of a. 10 reservoir R formed between the float. 4v and ,the reentrant member 41, by making the reentrant member 41- ofsmaller diameter at its innermost portion than at 'points farther removed from the shaft 13. This reservoir is of such size that the height of the column of mercury in the space 45 is maintained substantially constant irrespective of temperature chan e or of slight deformation of the stator cylinder 16, its-.reentrant -portion 41,

p' 2 or of the float 4 when under extreme pressure gradient at high operating speeds.

Mercury is lntroduced into the annularl space 45 and the reservoir R in measured quantity similar to the manner described with reference to F1gure 3. As machined, the annular ring 137 is prof vided withtwo stepped surfaces 146 and 147,

which correspond to the Hat surface of they y annular ring 145 andthe step 148 turned 3.0 upon the stator casing 16;` Between the annular ring 145 and the surface 146 I have provided a packing element 149 and between the surfaces 147. and 148 I have provided" a second packing 150. These packings serve 35 a similar purpose rto those designted 42 and 43v in Figure 3.

Referring again to .Figure 2 and the description. thereof, it is apparent that along ,the column 10 there is a gradation in pres- 0 sure, a greater'pressure being ata distance more removed from the center of rotation 3. Similarly; when the space 45, which surrounds float 4 and lies between the float 4 and the'stator casing 16 land the Heat 4 and ,'45 the reentrant member 41, is illed with mercury'and the lpropeller is' rotating at high speed, the -pressure gradient increases along the iioat as the distance of the particular section of the oat to be considered is` removed '50 1Jfrom the'center of' rotation of the shaft 13.

For this reason the bulkheads 139 are spaced 'at a less distance apart at the outer portion i of the float 4 than those near the/hub. l-Likewise, the stator member 16 and its reentrant @member 41 are thickened at their outer por# tions in order to. withstand thegreat pressure the mercury when the propeller is under rotation.

The rackshats 56 of Figure 6 are main- 50 tained inengagement withv the gear 26 ina manner'very similarto that shown and described with reference to Figures 3 to 6 with' the exception that the bosses 54 and the bearing therein are mounted' ldirectly upon the stator cylinderf16. i

.member slightly crankcase 50, 'as indicated at 157 in Figure 6. These elements are .unnecessary-to a propeller of my designunless it is to be used in re'io'n where the prevailing temperature is be ow that of 40 degrees below zero either Fahrenheit or centigrade, the solidifying temperature of mercury. Such 'a .device 'would be suicient to maintain the mercury in liquid form. Since this is merel an accessory to mg invention it is easily a a table to the modi ed form shown in Flgure and it is 'thought unnecessary todescribe it in detail with reference thereto.

The operation of my device is as f ollows: After the propeller starts turning, as soon as the centrlfugal force acting on the mercury reaches a value suicient to balance the attraction of gravit the mercury is thrown away from the possl le leak points under the esv washers. This occurs at :a very moderate speed-at fifty-four revolutions a minute, forv example, with the mercury moving around a two-foot circle.

As the speed of Arotation goes higher than this, it in exact proportion tothe centrifugal f orce builds up the hydrostatic pressure thatV lgushes centripetallyY against theend of the oat 4, to balance the centrifugal force which is acting to throw the blades outwardly, with 4their other attached weights.

' The centripetal eii'ect of the mercury is` designed to be suicient vmeasurabl to overbalance the blade and itsattache I which exerts a radial pressure, so that as soon as the mercuryfis thrown away from the rubber washers by a safe margin of speed, the centripetal force compresses this resilient and so retracts the washers off of their seats.

The amount of this retraction is designedly limited to a few thousandths of .an-inch.

A 'first effect of'this few thousandths movement is to eliminate the braking drag that the rubber washers oppose to angular rota-x tion of the blades whenthe propeller is not able-pitch andrreversible-blade propeller weights, and valso the tension of the'resilientfmember 'ico lrunning. Thus,contrary to all other varil schemes, with the propeller ofjmycinventio'n' the blades may It'urn freely at' any speed of propeller revolution, butrdo not so be turned when' it is not revolving.l Another andv most important effect of this inward movement of the blades, as my propeller starts revolving,

is vthat this movement can be made to impose 17'. -and 115, which has the eect of eliminating `all the possible lateral play 'or movement itv any desired thrust load on the bearings i f Vhub having areentra'nt portion, a liquid with,-

peller is revolved.

tion between the balls and theball races in this bearing. A ,factor which otherwiseA might cause serious blade lutterand vibration is thus eliminated.y

Itis to be noted that any vibration or flutter 'of the blade is opposed by the dashpot action of the mercury surrounding the float. This so that lateral movement ofthe blade andrits' ii'oat cannot occur without proportionate displacement of the mercury film which surrounds the float, which film', under the condition of 'centrifugal pressure prevailing in it,

out with the maximum resistance peculiar to a metal having a high density.

Thepitch'of the blades 1 may therefore be vIt will b'e understood that the above de` scription and accompanying drawings comprehend only the general and preferred embodiment rof my invention and` that detail changes in' the construction and arrangement of parts may be made within the scope of the appended claims withoutl sacrificing any Iof the advantages ofmy invention.

It is to be further understood that the ter mercury asuse' erein is to be construed to include liquid famalgams.

Having thus described my invention what Iclaimljsz- 'l s `1. In' a variable pitch propeller, the combination of a hub,"radiallymounted' angular; ly-rotatable blades mounted thereon, means within. thehb for 'carrying-a liquid, means upon the blade for' displacing aportionof said liquid- -whereby 'the liquid exerts a cen acting lthe centrifugal pressure thereof 'when under/revolution. I Y 2. In-fa variable-pitch propel1er,'the combination off a hub, radially-mounted angu# larly-rotatableblades mounted thereon, lsaid in the reent'rant portion,y and a float ilpon the blade and-extending within the reentrant portionto displace a portionof the-liquidwherejupon said blade substantially equal to the centrifugal pressure .thereof .whenthe pro`-- 3. In a variabler pitch propellenfthe' com- .65 -fb'ination of .'a hub, radially-mounted angu.`

of, alone or in conjunction with spring pres- Y sure similarly closes ,up all possible lost mo-v action is produced by the structure as shown together with its high mass `inertia-when theblade is .in rotation, opposes being squeezed' set at any desired angle by a slight movement tripetal pressure upon said blades counter-- by "the liquid exertsa centripetal pressure' veited position.

'larly-rotatable blades `mounted thereon, said hub having a reentrant portion, a small q-uantity of mercury retained within said hub by they reentrantlportion and a float upon the l blade and extending between the reentrant portion and the hub to displace a( portion of said mercury, whereby the mercury exerts a centripetal pressure upon the said blade substantially equal to the centrifugal pressure thereof when the propeller is revolved at operating speeds.

4. In a variable pitch propeller, the combination of radially extending blades, a iota-l tionv member surrounding the base of each blade ,and spaced. therefrom, a hub having mounting elements for each blade and reentrant members upon each of said'mounting elements, said reentrant members extending between the blade and its respective lotation member and a liquid between'the flotation member and the mounting element and its reentrant member.

` 5.111 a variable pitch propeller,.the combination of a hub, radially extending stator cylinders rigidly mounted thereon, reentrant members rigidly carried thereby and forming annular cups withsaid stator cylinders, liquid alignment with the annular cup, and annular `flotation members carried by lthe Shanks of said blades and extending within the annular.

.cup whereby a portion of the liquid therein -is displaced.

annular cup, and annular flotation ,members carried by the Shanks of 4said blades and extending within the annularcups whereby a portion ofthe liquid therein is displaced.

. 7. In a variable. pitch propeller, l.the combination" of a hub, radially extending stator cylinders rigidly mounted thereon, reentrant fme'mbersrigidly carried thereby and forming annular cups within said stator cylinders, the saidcups opening radially inward toward .within said annular cups, blades, the-Shanks fof which extendtoward -the hub in axial the hub,`a liquid' within said annular cups,

blades the Shanks of which extend` radially inward toward the huband through the ceintery of said annular' cup,'and means between the Kflotation members and the stator c asngs vand between the flotation members and the reenrant members whereby the liquid 'is retained within the annular cups when in in- .8. .In a propeller, the combination of radi allyLmounted'singularly-rotatable blades, otation elements mounted thereon and a liquid ias' 'while permittin yof the blades; liquid mercury films within said\bearings, the pressure within said `mersaid blade,

surrounding said flotation elements whereby the liquid when subjected to centrifugal force acting outwardly, produces a centripetal hydrostatic pressure, acting inwardly, upon said flotation elements to maintainsaid blade "inotation at operating speeds of revolution.

9. In a propeller with a hub and two or more blades, two or more vessels immovably aliixed to the hub and containing liquid mercury, and two or more floats and propeller blades securedthereto mounted in the' hub so as to be angularly-'rotatable, the" vessels and the floats being so shaped and disposed that the float in each vessel can rotate angularly within it,`whereby upon revolution of the propellery centrifugal force' acting upon the mercury in each vessel balances centrifugal force acting on the vfioat in the same vessel. v

10. In a variable-pitch or reversible blade propeller, with a hub and radially-mounted, v

angularly-rotatable blades; bearings for carrying the centrifugal load ofthe propeller the free angular rotation cury films automatically increasing by centrifugal force in substantially the same proplotion that the loads upon said mercury s are increased by centrifugal force acti ing upon the blade.

11. In a-variable pitch or reversible-blade air propeller. having a hub and radiallyplaced angularly rotatable blades; annular vessels or cups within said hub and surround ing said blades; an annular float element surrounding tand attached to each -blade and located within but not contacting with said annular cup or'vessel; anda mercury film surrounding said Ifloat within said cup or vessel; the designand configuration of said film being substantially lthat of a U.

12. In a variable pitch propeller, a hub, bearings therein, radially-mounted angularly-rotatable bladesv carried thereby and a single means between each blade' and said hub for relieving the centrifugal thrust of said blades upon'said bearings and substantially eliminatinglateral Hutter or vibration.

of said blades, said means consisting of a ble blades carried'thereby, means for'relieving the centrifugal thrust of said blades' upon sald bearings when said propeller rotatmg, said means consisting of a float carried by each of said blades, an annular cup within said hub and surrounding said oat, a film vof mercury within said cup and surrounding said ioat and means for angularly moving said yblades within said bearings when said propeller is revolving.

15. In -a variable-pitch -or reversiblevpropeller, the combination of a "hub, bearings therein, radially-mounted angularly-rotatavble blades carried thereby, means for relieving the centrifugal thrust said bearings when said propeller is revolving, said means consisting of .a float carried by each of said blades an annular cup within said hub and surrounding said float, mercury within said cup, a gear carried by each of said bades and means for angularly moving said b ades within said bearings, said means consisting of thrust element revolvable with said propeller, racks thereon and in engagement with said gears and means for moving said thrust element toward or away from said hub toangularly rotate saidblades within lsaid hub. v v

' VICTOR LOUGHEED.

of said blades upon iis float upon said blade, an annular cup within said hub arid surrounding said floatiand a cup and surrounding said liquid within said float. 13. In a, variable pitch propeller, a hub, bearings therein, radially mounted angularly-rotatable blades carried thereby and a single means between each blade and 'said hub -for relieving the centrifugal thrust of said 'blades upon said bearings andvsubstantially eliminating lateral flutter or vibration of said blades, said means consistingof a float upon anannular cup within said hub and surrounding said float and a film of,- 

